There are currently four cholesterol lowering medications in the class called HMGCoA reductase inhibitors approved by the FDA and available for use. The newest medication in this class, called Atorvastatin, was approved as safe and effective for use in the past year by the FDA. This study will randomize patients with coronary artery disease, to either treatment with the new drug Atorvastatin, or an older drug, Simvastatin, for 1 year. Blood cholesterol lowering will be compared between the two medications.